Phycobiliproteins are now used as fluorescent labels in a variety of applications. A major problem with their use is their high molecular weights. This project focuses on a small group of algae, the cryptomonads, that produce smaller phycobiliproteins as a possible source of new labels. This Phase II research will continue the previous efforts to produce a broad range of phycobiliproteins that have much smaller molecular weights than those currently available. The Phase I study successfully produced a pigment, Cr-PE545, that has different spectral and fluorescent properties, will form a stable conjugate with streptavidin that retains the interesting fluorescent properties. There are five other of the small phycobiliproteins reported in the literature, and we have found strains that produce four of these. During Phase II, the other four will be developed and the last one located. In addition, we will attempt to break down the holoproteins into constituent subunits, all of which contain one or several chromophores. These will then be evaluated for utilization as possible fluorescent labels. A by-product might also hold promise as a potential dye. Chlorophyll c is produced by these algae and could be harvested as a by-product from residual biomass. Peridinium chlorophyll a protein has been used as a fluorescent probe in flow cytometry. We will evaluate the potential of these unique chlorophylls for this purpose. The goal of this research is to provide a large array of new and unique pigments for use as fluorescent labels. We have already been successful with one of the small phycobiliprotein, and see the Phase B research as a way to develop an expanded range of phycobiliproteins.